1. Field
The embodiments described herein are related to wireless communication and more particular to implementation of a data control channel that provides information related to how to receive a traffic channel in a wireless communication system.
2. Background
It will be understood that in a wireless communication system certain traffic channels are used to communicate data, e.g., between a base station or wireless access point and a wireless communication device. It will also be understood that a data control channel is usually associated with a traffic channel. The data control channel is used to communicate information that allows either the base station or wireless communication device to receive and decode data on the traffic channel correctly. For example, a channel termed the preamble channel is the data control channel in systems that implement the cdma2000 Evolution Data Optimized (EV-DO) standards and protocols for the Forward link. Similarly, the Reverse Rate Indicator (RRI) channel is the data control channel in cdma2000 EV-DO systems for the reverse link. These channels are described in the 3GPP2 C.S0024-A v2.0 standard. In a Wideband Code Division Multiple Access (WCDMA) system, the High Speed-Shared Control Channel (HS-SCCH) is the data control channel in the downlink, while the Enhanced Dedicated Physical Control Channel (E-DPCCH) is the data control channel in the uplink.
Depending on the system, the data control channel can be transmitted either simultaneously with or in advance of the corresponding traffic data channel.
The term “wireless communication device” as used in this description and the claims that follow is intended to refer to any device capable of wireless communication with, e.g., a base station or wireless access point. Thus, the term “wireless communication device” includes, but is not limited to, cellular telephone type devices, also known as handsets, mobiles, mobile handsets, mobile communication devices, etc., Personal Digital Assistants (PDAs) with wireless communication capability, smartphones, computing devices with wireless communication capability including handheld computers, laptops, or even desktop computers, etc.
It will also be understood that while many of the examples and embodiments provided herein refer to Wireless Wide Area Networks (WWANs), the systems and methods described herein can also be applied to Wireless Personal Area Networks (WPANs), Wireless Local Area Networks (WLANs), Wireless Metropolitan Area Networks (WMANs), etc. It will also be understood that such networks include some type of access device or infrastructure such as a base station, e.g., in a WWAN or WMAN, or an access point, e.g., in a WLAN. It will be understood therefore that reference to these access devices/infrastructures are interchangeable and that reference to one should not exclude reference to another unless explicitly stated or where such is dictated by the context of the reference.
As noted, the information contained in the data control channel is used by the receiver to correctly receive and decode data on the traffic channel. Thus, the reliable detection of the data control channel is crucial for data reception performance; however, the data control channel must also be received and decoded correctly. Accordingly, the decoding performance for the data control channel should exceed that for other channels in order to ensure that the critical control information is received properly. It will be understood that increased performance usually requires increased resources and/or overhead. Increased overhead, however, can have a negative impact on the transmission efficiency.
In conventional systems, the number of bits that are carried by the data control channel is relatively small. In future wireless communication systems, however, the number of bits will likely increase due to the increased complexity of the system design. Even with the existing EV-DO preamble design, the forward link performance is limited by the preamble in certain radio channel conditions, such as a one-path slow fading conditions. Current system architectures with respect to the data control channel can result in large frame error rates or reduced transmission efficiency in such conditions.
For example, a cdma2000 EV-DO system uses bi-orthogonal coding for the forward link preamble. Thus, if 10 bits need to be transmitted, the data control channel, i.e., preamble in forward link, requires at least 512 symbols. Accordingly, it should be apparent that current systems impose large overhead requirements even when transmitting just a few bits of information. For example, the 512 symbols of this example will use too much of the resource, e.g., for a wireless communication device with high Channel to Interference (C/I) ratio. At the same time, however, the channel codes used in conventional data control channels are not very powerful, or the inclusion of required tail bits reduces transmission efficiency. Thus, large amount of resources are being consumed, even though somewhat limited performance gain is being provided via conventional data control channels.